1. Field of the Invention
The present invention relates to a soft mold, a method of manufacturing the same and a patterning method using the same, and more particularly, to a soft mold, the lifetime of which is extended, a method of manufacturing the same and a patterning method using the same.
2. Discussion of the Related Art
As semiconductor devices are scaled down and highly integrated, the technology of forming a pattern to enhance new functions has attracted considerable attention. The lithography technology is one kind of patterning technology that has become a core technology in fabricating semiconductor devices. Currently, suggested various methods are capable of economically embodying a nano-scale pattern as well as a micro-scale pattern using simplified processes.
However, current nano-patterning technology with high integration degree demands high technology expense in view of apparatus and processes therefor. Moreover, there is a physical limitation in using a polymer material formed of a conventional photosensitizer, and also some problems such as low patterning speed, poor resolution, difficulty in being applicable to a curved surface, etc. Therefore, in order to resolve these problems, a soft-lithography technology has been proposed, which is different from the typical photolithography technology.
According to the soft-lithography technology, a pattern or a structure is formed by repeatedly smearing an organic material on a soft polymer stamp without utilizing light or high-energy particles. That is, the pattern is transferred onto a synthetic resin or the like by smearing predetermined ink on the polymer stamp. Herein, one of polymer materials acting as the polymer stamp is PolyDiMethylSiloxane (PDMS). In the typical photolithography technology, complicated etching processes should be repeatedly performed. However, using PDMS enables the processes to be simple, wherein the PDMS can be easily applied to a specific region such as a large area portion or a curved surface, and also it is possible to selectively coat a thin film.
FIGS. 1A to 1C are sectional views illustrating a method of forming a pattern using a PDMS mold according to the related art. As shown in FIG. 1A, a substrate 560 is coated with a resin layer 550a, and then a PDMS mold 510 with a predetermined pattern is deposited on the resin layer 550a. Herein, the predetermined pattern of the PDMS mold 510 has a concave-and-convex shape. As shown in FIG. 1B, the PDMS mold 510 is brought into contact with the coated resin layer 550a, thereby transferring the predetermined pattern onto the coated resin layer 550a to form a resin layer 550. Thus, the resin layer 550 has a convex-and-concave pattern. In general, both the organic material in the polymer and the organic material in the transited object have hydrophobic properties.
As illustrated in FIG. 1B, during the process of using the PDMS mold 510 to transfer the pattern, the surface of the PDMS mold 510 is gradually damaged due to the PDMS mold 510 continuously contacting the coated resin layer 550a. For this reason, CH— is easily separated from the surface of the PDMS mold 510, which may occur locally or broadly at the surface of the PDMS mold 510. Thus, when the PDMS mold 510 is repeatedly utilized, a material exchange occurs between the PDMS mold 510 and the coated resin layer 550a. 
As shown in FIG. 1C, the coated resin layer 550a is changed into the patterned resin layer 550 having the predetermined pattern of the PDMS mold 510 by contacting the PDMS mold 510 with the coated resin layer 550a. Like the process as illustrated in FIG. 1B, as the number of times of utilizing the PDMS mold 510 increases, the material exchange occurs between the PDMS mold 510 and the patterned resin layer 550. Thus, the surface of the patterned resin layer 550 formed by the PDMS mold 510, which has been repeatedly utilized, tends to be hydrophobic. Accordingly, it impossible to form another organic layer on the patterned resin layer 550 because a wetting contact angle cannot be formed.
FIG. 2 is a graph illustrating a relationship between contact angle variations of the patterned resin surface and the number of times of utilizing the PDMS mold according to the related art. As illustrated in FIG. 2 in view of FIGS. 1A to 1C, a dashed line A represents an intrinsic contact angle of the coated resin layer 550a. In a predetermined range from the dashed line A to a dashed line B, as the number of times of utilizing the PDMS mold 510 increases, the contact angle becomes higher because more CH— is easily separated from the surface of the PDMS mold 510, thereby causing the PDMS mold 510 to be gradually hydrophobic. Thus, when the PDMS mold 510 is repeatedly utilized, the material exchange occurs between the PDMS mold 510 and the resin layer 550. As a result, the surface of the PDMS mold 510 becomes hydrophobic.
Even if the contact angle of the PDMS mold 510 increases and the material exchange actively occurs between the PDMS mold 510 and the resin layer 550, as long as the contact angle is within the predetermined range from the dashed line A to the dashed line B of FIG. 2, it is possible, in light of a surface condition of the resin layer 550, to form another organic layer on the resin layer 550 because the organic layer and the resin 550 may contact well with each other within this contact angle range. However, if the contact angle is in a range from the dashed line B to a dashed line C of FIG. 2, since the wetting contact angle cannot be formed in light of the surface condition of the resin layer 550, it is difficult to form another organic layer on the resin layer 550, thereby making it impossible to perform a thin film process after all.
In conclusion, as the number of times of utilizing the PDMS mold 510 increases, the PDMS mold 510 becomes hydrophobic because CH— is separated from the surface thereof. Further, since no wetting contact angle is formed, another organic layer cannot be formed on the patterned resin layer 550. As a result, the resin layer 550 having the pattern transferred by the PDMS mold 510 cannot maintain its predetermined contact angle, thereby making it impossible to form another organic layer on the patterned resin layer 550. After all, the PDMS mold 510 cannot be repeatedly utilized because the repeat utilization makes the PDMS mold 510 hydrophobic.